Interferon-τ -induced ISG15-AS regulates endometrial receptivity during early goat pregnancy

Endometrial receptivity is a critical process for the successful establishment of pregnancy in ruminants. However, the biological role of long non-coding RNAs (lncRNAs) in the development of endometrial receptivity is poorly understood. In this study, we performed RNA-seq analysis of immortalised goat endometrial epithelial cells (gEECs) treated with interferon-τ (IFNT). Transcriptome profiles showed that 8069 high-confidence putative lncRNAs, including 6498 intronic lncRNA transcripts, 1078 lincRNAs and 493 antisense lncRNAs were identified in gEECs with or without IFNT treatment. Functional clustering analysis was performed by using cis and trans lncRNAs prediction. GO and KEGG analyses revealed that differentially expressed lncRNAs may regulate tissue remodelling and immune responses. Subsequently, six of the 21 differentially expressed antisense lncRNAs were validated using qRT-PCR. Through functional screening and co-expression analysis of lncRNAs in gEECs, we identified that ISG15-AS was mainly expressed in the luminal and glandular epithelium on days 5 and 15 and was strongly upregulated on day 18 of pregnancy in vivo. Similarly, ISG15-AS was abundant in the nucleus and cytoplasm, and was significantly upregulated after treatment with IFNT in gEECs. In addition, ISG15 is an IFNT-responsive gene, that displayed an evident increase in vivo and in vitro. Moreover, sense ISG15 was significantly upregulated following ISG15-AS silencing. The key genes related to ISGylation and endometrial receptivity in gEECs dramatically increased after ISG15-AS inhibition. Collectively, our results indicate that a novel antisense lncRNA, ISG15-AS, may be important in regulating endometrial receptivity through ISGylation.